This invention relates to a method and apparatus for the continuous production of silicon oxide powder.
In the prior art, silicon oxide powder is produced, as disclosed in JP-A 63-103815, by heat treating a raw material mixture containing silicon dioxide base oxide powder in a reduced pressure, non-oxidizing atmosphere to generate SiO vapor, and condensing the SiO vapor in a gas phase, thereby continuously forming fine amorphous SiO particles with a size of 0.1 xcexcm or less. Alternatively, silicon raw material is heated, evaporated and deposited on a surface of a substrate having a coarse structure as disclosed in JP-A 9-110412.
The method of JP-A 63-103815 is capable of continuous production, but fails to produce high purity silicon oxide powder because the SiO powder produced is a fine powder which undergoes oxidization when taken out in the air. The method of JP-A 9-110412 can produce high purity silicon oxide powder, but does not lend itself to mass-scale production since it is of batchwise design. As a consequence, the silicon oxide powder becomes expensive.
An object of the invention is to provide a method and apparatus for the continuous and effective production of high purity silicon oxide powder at a low cost.
It has been found that a silicon oxide powder can be continuously prepared by feeding a raw material powder mixture containing at least silicon dioxide powder into a reaction furnace heated at a temperature of 1,100 to 1,600xc2x0 C., to produce a silicon oxide vapor, transferring the silicon oxide vapor to a deposition chamber through a transfer conduit maintained at a temperature of from higher than 1,000xc2x0 C. to 1,300xc2x0 C., causing silicon oxide to deposit on a surface of a substrate which is disposed and cooled in the deposition chamber, scraping the silicon oxide deposit at desired intervals, and recovering the silicon oxide in a recovery chamber.
According to one aspect of the invention, there is provided a method for continuously preparing a silicon oxide powder, comprising the steps of feeding a raw material powder mixture containing silicon dioxide powder into a reaction furnace; heating the mixture in the furnace in an inert gas or in vacuum to a temperature of 1,100 to 1,600xc2x0 C. to produce a silicon oxide gas; introducing the silicon oxide gas into a cooling chamber through a transfer conduit which is maintained at a temperature of from higher than 1,000xc2x0 C. to 1,300xc2x0 C., thereby causing silicon oxide to deposit on a surface of a substrate which is disposed and cooled in the cooling chamber; and continuously recovering the silicon oxide deposit.
According to another aspect of the invention, there is provided an apparatus for continuously preparing a silicon oxide powder, comprising a charge feed means for feeding a raw material powder mixture containing silicon dioxide powder to a reaction chamber; the reaction chamber where the raw material powder mixture is reacted to produce a silicon oxide gas; a transfer line for transferring the silicon oxide gas from the reaction chamber to a deposition chamber; the deposition chamber in which a substrate is disposed and cooled so that silicon oxide deposits on a surface of the cooled substrate; and a recovery means for recovering the silicon oxide deposit on the substrate.